Number two was CharlesSchwab.com – which had tied with Fidelity at the top in 2006 - while TD Ameritrade came in at number three.

Overall, the report said customers are increasingly satisfied with the online brokerage industry. Their satisfaction is partly driven by perceived improvements in online security. But they are also getting progressively used to the convenience of conducting transactions online.

"Consumers are increasingly accustomed to the ease and convenience of conducting transactions online, and the stellar scores of the top three (all multichannel institutions) highlight the strides made in making customers comfortable with online security," said Larry Freed, president and CEO of ForeSee Results and author of the ACSI E-Commerce Report.

Meanwhile, E*Trade ranked at the bottom of the list of customer satisfaction. Freed suggested this may reflect the brokerage's presence as an online-only investment company.

"It has not established the long and trusted reputation that the other three have achieved in the offline world," he said in the report, which also covered e-retail and online travel companies.

"E*Trade attempts to distinguish itself by highlighting ease of transactions, but customers seem to prefer more established companies," he said.

But Freed said E*Trade also suffered from the bad publicity it received after reporting losses of $18 million as a result of customer account breaches. (Although TD Ameritrade also suffered a data breach in 2007).

Nevertheless, E*Trade has overall registered a 10.6% rise in its customer satisfaction score since 2000.